U.S. patent number 4,002,796 [Application Number 05/540,164] was granted by the patent office on 1977-01-11 for conditioning of polyolefinic fibers for use in the manufacture of synthetic paper.
This patent grant is currently assigned to Montedison Fibre S.p.A.. Invention is credited to Luciano Baldi, Emilio Martini.
United States Patent |
4,002,796 |
Baldi , et al. |
January 11, 1977 |
Conditioning of polyolefinic fibers for use in the manufacture of
synthetic paper
Abstract
Polyolefinic fibers for use in the manufacture of synthetic
paper are rendered readily water-dispersible by pre-treatment with
a hydrophilic polymer which is a condensate of polyvinyl alcohol
and aliphatic aldehydes containing from 1 to 6 carbon atoms, which
condensates contain from 2 to 8 aldehyde residues per 100 units of
polyvinyl alcohol.
Inventors: |
Baldi; Luciano (Turin,
IT), Martini; Emilio (Bologna, IT) |
Assignee: |
Montedison Fibre S.p.A. (Milan,
IT)
|
Family
ID: |
11156778 |
Appl.
No.: |
05/540,164 |
Filed: |
January 10, 1975 |
Foreign Application Priority Data
|
|
|
|
|
Jan 11, 1974 [IT] |
|
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19329/74 |
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Current U.S.
Class: |
428/375; 428/378;
428/394; 525/57; 427/389.9; 428/516; 525/61 |
Current CPC
Class: |
D21H
13/14 (20130101); D21H 5/1254 (20130101); D21H
17/50 (20130101); D06M 15/347 (20130101); Y10T
428/31913 (20150401); D06M 2200/00 (20130101); Y10T
428/2933 (20150115); Y10T 428/2938 (20150115); Y10T
428/2967 (20150115); D06M 2101/20 (20130101) |
Current International
Class: |
D06M
15/347 (20060101); D06M 15/21 (20060101); D06M
015/08 () |
Field of
Search: |
;260/897
;428/375,378,394 |
References Cited
[Referenced By]
U.S. Patent Documents
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|
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3090769 |
May 1963 |
Coover et al. |
3226455 |
December 1975 |
Matsubayashi et al. |
3848027 |
November 1974 |
Forbess et al. |
|
Foreign Patent Documents
Primary Examiner: Seccuro; Carman J.
Claims
We claim:
1. In the process of rendering polyolefin fibers having a surface
area greater than 1 m.sup.2 /g dispersible in water which comprises
treating said polyolefin fibers with an aqueous solution of a
hydrophilic polymer, the improvement characterized in that the
hydrophilic polymer is a condensation product of polyvinyl alcohol
with an aliphatic aldehyde having from 1 to 6 carbon atoms which
condensation product contains, in the macromolecule, from 2 to 8
aldehyde residues per 100 vinyl monomeric units.
2. The improvement according to claim 1, further characterized in
that the polyvinyl alcohol/aliphatic aldehyde condensate contains,
in the macromolecule, from 4 to 6 aldehyde residues per 100 vinyl
monomeric units.
3. The improvement according to claim 1, further characterized in
that the hydrophilic polymer is a condensation product of polyvinyl
alcohol and propionic aldehyde.
4. The improvement according to claim 1, further characterized in
that the hydrophilic polymer is a condensation product of polyvinyl
alcohol and butyric aldehyde.
5. Polyolefin fibers having a surface area greater than 1 m.sup.2
/g and, having fixed thereon a hydrophilic polymer which renders
the fibers readily dispersible in water, by treating said fibers
with an aqueous solution of said hydrophilic polymer which is a
condensation product of polyvinyl alcohol and an aliphatic aldehyde
containing from 1 to 6 carbon atoms, said condensate containing, in
the macromolecule, from 2 to 8 aldehyde residues per 100 vinyl
monomeric units.
6. Polyethylene fibers according to claim 5.
7. Polypropylene fibers according to claim 5.
Description
THE PRIOR ART
It is known that, starting with polyolefins, and in particular with
polyethylene or polypropylene, it is possible to obtain
microfibers, or fibers, having morphological characteristics rather
similar to those of cellulose fibers, and which can be substituted,
wholly or partially, for cellulose fibers in the manufacture of
paper.
In general, such fibers, which are known as fibrils or fibrides,
have a length of from 1 to 50 mm., an average diameter of from 1 to
400 microns, and a surface area (specific surface) larger than 1
m.sup.2 /g.
A process for obtaining such fibrils or fibrides, and use thereof
in the manufacture of semi-synthetic paper are disclosed in the
pending application of Paolo Galli et al Ser. No. 335,335 filed
Feb. 23, 1973.
According to that process, the fibrils or fibrides are obtained by
extruding a solution of the polyolefin at a temperature higher than
the boiling point of the solvent and at autogenous or higher
pressure into a zone of lower pressure and hitting the extruded
solution, at an angle with respect to the direction of extrusion
thereof, with a jet of fluid having a temperature lower than that
of the extruded solution.
Other methods for obtaining fibrils or fibrides of synthetic
polymers suitable for replacing cellulose fibers in the manufacture
of paper, or for making paper or paper-like products are disclosed,
f.i., in USP 2,999,788 in British Pat. No. 1,262,531 and in German
Patent Publications DT-OS No. 1,951,576.5 and DAS No.
1,290,040.
In order to use synthetic fibers successfully in the manufacture of
synthetic or semi-synthetic paper having satisfactory homogeneity
and strength on conventional paper-making equipment and by
conventional paper-making techniques it is essential that the
synthetic fibers have a dispersibility in water similar to that of
cellulose fibers which, due to their morphology and chemical nature
disperse very readily and homogeneously in water.
As is known, the fibrils or fibrides of water-repellent synthetic
polymers, such as the polyolefins, are not normally easily
dispersed in water. Improvement in the water-dispersibility of the
fibrils and fibrides thereof requires a pre-treatment which results
in the presence of hydrophilic groups on the surface of the fibrils
or fibrides.
Various methods are available for solving the problem, e.g.,
surface modification of the fibrils or fibrides by chemical
treatment, intimate mixing of the polyolefin with surfactants or
with polymers containing hydrophilic groups; or surface coating of
the pre-formed fibrils or fibrides with hydrophilic polymers.
The method involving coating the synthetic fibrils or fibrides with
a hydrophilic polymer has proved preferable in practice. That is
because aqueous solutions of hydrophilic polymers are always at
least partially colloidal and when an aqueous solution thereof is
contacted with the hydrophobic synthetic fibrils having a large
surface area a certain amount of the hydrophilic polymer is
absorbed on the surfaces of the synthetic fibers and facilitates
dispersion of the coated fibers in aqueous media. For commercial
scale operations, it is important for the absorption to occur in a
short time.
According to German Pat. No. 2,208,555, hydrophilic polymers
suitable for coating the synthetic fibers are aminic resins,
polyethylenimines, polypyrrolidone and polyamides modified by
epichlorhydrin. In Belgian Patent No. 787,060 polyvinyl alcohol is
suggested for use as the hydrophilic polymer.
According to the German and Belgian patents, the synthetic fibers
are dispersed in an aqueous medium containing the hydrophilic
coating polymer and, optionally, solvents and/or binders of various
types, and the suspension is converted to paper in accordance with
the traditional technology. The Belgian patent also contemplates
concentration of the aqueous suspension for transportation and
re-dispersion during manufacture of the paper.
THE PRESENT INVENTION
An object of this invention is an improvement in the prior art
concerned with improving the water-dispersibility of polyolefinic
fibrils or fibrides by coating the same with a hydrophilic polymer
whereby there are attained higher absorption kinetics and the
fixing of an increased amount of hydrophilic material on
polyolefinic fibers from aqueous solutions of the hydrophilic
material whereby the velocity of dispersion of the polyolefinic
fibers in water is considerably enhanced.
Those and other objects are accomplished by this invention in
accordance with which the polyolefinic fibrils or fibrides are
treated with an aqueous solution of a hydrophilic material
resulting from the condensation (or acetalizing) of polyvinyl
alcohol with an aliphatic aldehyde containing from 1 to 6 carbon
atoms, which condensation products contain, in the macromolecules,
from 2 to 8, preferably from 4 to 6, aldehyde residues per 100
monomeric polyvinyl alcohol units.
The polyvinyl alcohol/aliphatic aldehyde condensates used in the
present process and methods for preparing them are known in the
patent and technical literature. See, for example, French Pat. No.
850,891 and "Polyvinylalkohole," by F. Kainer, published by F.
Enke-Stuttgart, 1949, pp. 63 - 80.
In one method of preparing the condensates, and which has been
employed in reducing this invention to practice, polyvinyl alcohol
is reacted, for some hours, with between 1% and 10% by weight of
the aldehyde based on the polyvinyl alcohol weight, at temperatures
preferably below 50.degree. C, in methyl or ethyl alcohol, and
subsequently the solid condensation product formed is separated
from the reaction mixture by centrifuging.
For achieving the objects of this invention there can be used the
condensates of polyvinyl alcohol with formic, acetic, propionic or
butyric aldehyde, aldol or mixtures of the same.
The polyolefinic fibers can be effectively coated by dipping them
into an aqueous solution of the polyvinyl alcohol/aldehyde
condensate having a condensate concentration of 0.01 - 0.1% by
weight, a temperature not higher than 100.degree. C, and kept under
agitation. Under those conditions, the residence time of the fibers
in the solution required to insure effective coating of the fibers
with the condensate and rapid dispersion in the aqueous medium may
vary from 5 to 30 minutes.
The suspension of coated fibers thus obtained can be used as such
to prepare pulps which, on the addition of cellulose fibers, can be
converted to semi-synthetic paper. More profitably, the suspensions
can be used, after filtration and partial drying, to prepare panels
of the polyolefinic fibers which are readily storable and
transportable and which are readily dispersible in water at the
time of their utilization in paper mills.
The following examples are given to illustrate the invention and
are not intended to be limiting. For instance, the polyolefinic
fibrils used in the examples were prepared -- as described below --
by the process disclosed in the pending Galli et al application
Ser. No. 335,335 (supra) although, obviously, the invention is not
limited to coating the fibrils or fibrides so obtained but can be
applied to all fibers based on olefinic polymers however obtained
and which are suitable as total or partial replacement for
cellulose fibers in the manufacture of paper and paper-like
articles.
Preparation of polypropylene fibrils
A 50 l autoclave, provided with heating chamber and stirrer, was
fed with 2.3 kg of polypropylene (density = 0.91; melting index =
10; melting point = 170.degree. C; isotacticity index = 94) along
with 30 l of n-pentane. The mixture was heated to obtain a solution
of the polymer in the n-pentane, under the following
conditions:
temperature = 170.degree. C
pressure = 20 kg/cm.sup.2
Under such conditions, the solution was ejected to the atmosphere,
through a circular nozzle having a 2 mm diameter, and was made to
collide, at about 1 mm distance from the outlet of the nozzle, with
a dry saturated steam jet, coming from a nozzle of 4 mm diameter
and arranged at an angle of about 85.degree. to the direction of
ejection of the polymeric solution, at an impact speed of about 470
m/sec.
A fibrous product was obtained which, under the optical microscope,
proved to be composed of individual fibrils having a length
comprised between 3 and 5 mm and an apparent (average) diameter of
about 10 microns; their surface area (specific surface) was 5
m.sup.2 /g.
Preparation of polyethylene fibrils
By using the same apparatus as was used to obtain the polypropylene
fibrils, polyethylene fibrils were prepared starting from a
solution of 3 kg of polyethylene (melting index = 5, melting point
= 135.degree. C, density = 0.95) in 35 l of n-hexane, kept under
the following conditions;
temperature = 180.degree. C
pressure = 9 kg/cm.sup.2,
using, as disrupting fluid, dry saturated steam under the same
conditions and according to the same modalities as described for
the preparation of the polypropylene fibrils. The polyethylene
fibrils thus obtained, had a length ranging from 3 to 5 mm, an
apparent diameter of about 10 microns and a surface area of 7
m.sup.2 /g.
EXAMPLE 1
10 g of polyvinyl alcohol, having a hydrolysis degree = 98-100 and
a Hoeppler viscosity, at 20.degree. C in a 4% aqueous solution,
equal to 22 - 28 cP, were mixed with 70 g of methyl alcohol and the
resulting mixture was acidified with 0.2 g of concentrated
sulphuric acid. 0.5 g of butyric aldehyde were then added and the
whole was reacted under stirring for about 2 hours at a temperature
of approx. 40.degree. C. A polyvinyl alcohol/butyric aldehyde
condensate was obtained and separated from the reaction mixture by
centrifuging. On analysis, it was found to contain 4.5 aldehyde
residues per 100 units of vinyl monomer.
0.59 g of the condensate were dissolved in 2.5 l of water
(concentration = 236 ppm) and the solution was heated to 90.degree.
C. Under stirring, 50 g of the polypropylene fibrils, prepared
according to the process described above, were added to the
solution. After 15 minutes, the fibrils were recovered by
filtration, and the amount of residual condensate determined on the
mother liquors by the method of W. T. Brown et al, Am. Dyestuff.
Rep., Sept. 1967, p. 36. The found value is reported in Table I,
along with the calculated percentage values of retention (% of
fixed condensate/condensate pre-existing in the bath) and of the
condensate amount fixed on the fibrils.
EXAMPLE 2
A condensate of polyvinyl alcohol and propionic aldehyde having a
content of 6 aldehyde residues per 100 vinyl monomeric units was
prepared, by operating according to the same modalities as in
Example 1 to obtain the butyric derivative, and employing 0.4 g of
propionic aldehyde for 10 g of polyvinyl alcohol in the
reaction.
By following modalities analogous to those of Example 1 and using
an aqueous solution containing 208 ppm of the condensation
propionic derivative, 50 g of the polyethylene fibrils prepared as
described above were coated. The relevant results are reported in
Table I.
EXAMPLE 3
50 g of the polyethylene fibrils were coated by operating under
conditions and according to modalities analogous to those of
Example 1, but utilizing an aqueous bath containing 390 ppm of the
same polyvinyl alcohol/butyric aldehyde condensate. The results
obtained are reported in Table I.
EXAMPLE 4
50 g of the polyethylene fibrils were coated by operating under
conditions and according to modalities analogous to those of
Example 1, but utilizing an aqueous solution containing 240 ppm of
polyvinyl alcohol/butyric aldehyde condensate containing in the
macromolecule 4.2 aldehyde residues per 100 vinyl monomeric units.
The results obtained are reported in summarizing Table I.
EXAMPLE 5 (comparative)
0.55 g of polyvinyl alcohol having a hydrolysis degree = 98-100 and
a Hoeppler viscosity (measured in a 4% aqueous solution at
20.degree. C) = 22-28 cP, were dissolved in 2.5 l of water.
The solution, containing 220 ppm of polyvinyl alcohol, was heated
to 90.degree. C and, under stirring, 50 g of the polyethylene
fibrils obtained as described above were added thereto. After 15
minutes the fibrils were recovered by filtration. The results are
reported in Table I.
EXAMPLE 6 (comparative)
Comparative Example 5 was repeated, but using an aqueous solution
containing 400 ppm of polyvinyl alcohol. The results are reported
in Table I.
EXAMPLE 7 (comparative)
Operating as in comparative Example 5, but using 0.59 g of
polyvinyl alcohol as such (having a hydrolysis degree = 86-89 and a
Hoeppler viscosity in a 4% aqueous solution at 20.degree. C = 22-28
cP) in 2.5 l of water (concentration = 236 ppm). The results are
reported in Table I.
TABLE I
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Examples 1 2 3 4 5 6 7 Bath temperature (.degree. C) 90 90 90 90 90
90 90 Time required by the fibers treatment (min.) 15 15 15 15 15
15 15 Initial concentration of the modifier in the bath (ppm) 236
208 390 240 220 400 236 Final concentration of the modifier in the
bath (ppm) 110 67 215 77 180 363 142 Retention (%) 53.4 67.8 44.9
68 18.2 9.3 39.9 Fixed modifier per 100 g of fibers (g) 0.62 0.66
0.90 0.81 0.19 0.18 0.47
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